1. Technical Field of the Invention
The present invention generally relates to a suspension component for an automobile. More specifically, the present invention relates to a stabilizer bar having localized material strengthening, and a method of manufacturing the stabilizer bar.
2. Description of the Prior Art
In an automotive vehicle, suspension components, such as a stabilizer bar, helps to keep the vehicle level, particularly when the vehicle is traveling through a curve. The ends of the stabilizer bar are connected to the right and left wheel assemblies of the vehicle. A pair of brackets, positioned between the ends of the stabilizer bar, secure the stabilizer bar to a structural component of the vehicle. Rubber bushings positioned between the stabilizer bar and the brackets provide limited torsional, axial and radial movement of the stabilizer bar relative to the bracket. The rubber bushings also dampen the movement of the stabilizer bar.
Typically, the goal of the material selection and manufacturing process used to make a stabilizer bar is to form a stabilizer bar with homogenous material properties that meet the highest required yield and fatigue strengths, as determined by calculated finite element analysis procedures. In many cases, cold forming, hot forming, heat treatments, and shot peening operation are performed on the stabilizer bar to achieve the yield and fatigue strength properties. The heat treatments must be applied to the entire stabilizer bar.
In actual use the highest stresses within the stabilizer bar are realized in specific localized areas along the stabilizer bar, not along the entire length. Therefore, stabilizer bars made by more traditional methods, where the entire stabilizer bar is heat treated, present several disadvantages. One disadvantage is that the stabilizer bar is heavier than it needs to be, because the stabilizer bar is homogenous. Another disadvantage is that the process involves unnecessary cost, as the entire stabilizer bar is subjected to heat treatment, when only a localized area must meet the high stress requirements. Finally, the facilities needed to process the stabilizer bar are larger, and require more energy, than needed, because they must be adapted to treat the entire stabilizer bar.
Additionally, typical manufacturing methods for suspension components such as stabilizer bars include heating the bar to a high temperature, bending the bar to the desired shape, and then quenching and tempering the bar. These steps are typically required to maintain the strength of the bar after the bar is bent. Quenching and tempering, however, causes de-carbonization of the entire bar and deformation of the bar, which must be later corrected.
Therefore, there is a need for an improved stabilizer bar, made from a material that can be cold formed to the required shape without requiring heating, quenching and tempering operations, and that includes localized area that are treated to withstand high stresses. Further, there is a need for an improved method of forming a suspension component that allows the suspension component to be cold formed to the required shape and to have localized areas that are treated to withstand high stresses, while the remaining areas of the suspension component are not treated.
A principle object of this invention is to provide a suspension component that is made from a material that can be cold formed to the needed shape and can be cold work hardening strengthened or heat treated to withstand stress levels that will be experienced by the suspension component.
Another object of this invention is to provide a suspension component that has localized portions that are specially treated with cold work hardening, shot peening and/or heat treatment to withstand localized stresses that the suspension component will experience, while the remaining portions of the suspension component remain untreated.
It is also an object of this invention to provide a method of manufacturing a suspension component having localized portions that are work hardening strengthened, shot peened or heat treated to withstand localized stresses that the suspension component will experience, while the remaining portions of the suspension component remain untreated.